Re: Re: wo did some test on cassandra ,but the result puzzled us

[Jonathan Ellis]

yes, this is a single-threaded benchmark so if getRandomRow is slow at
all, it is going to skew the hell out of your results :)

2010/3/12 Bingbing Liu <rucb...@gmail.com>:
> the difference between se and random the test code is just how the key of 
> each record is generated.
>
> the test code is :
>
>
> long totalSWriteTime = 0;
> for (int i = 0; i < totalRows; i++) {
> byte[] key = dg.getRandomRow();//when sequential write , we use i as the key
> byte[] data = dg.generateValue();
> long start = System.currentTimeMillis();
> client.insert("Keyspace1", new String(key), new ColumnPath(
> "Standard1", null, "data".getBytes("UTF-8")), data,timestamp, 
> ConsistencyLevel.ONE);
> totalSWriteTime += (System.currentTimeMillis() - start);
>    if(i % 10000 == 0){
> System.out.println("Has write " + i);
>    }
> }
>
> is there something wrong?
> 2010-03-12
>
>
>
> Bingbing Liu
>
>
>
> 发件人： Jonathan Ellis
> 发送时间： 2010-03-12  13:40:40
> 收件人： cassandra-dev
> 抄送：
> 主题： Re: wo did some test on cassandra ,but the result puzzled us
>
> why reads are slower than writes:
> http://wiki.apache.org/cassandra/FAQ#reads_slower_writes
> no idea on seq vs random.  i would not be surprised if there is a bug
> in your test code.
> On Fri, Mar 12, 2010 at 12:36 AM, Bingbing Liu <rucb...@gmail.com> wrote:
>> We did some test on on Cassandra, and the benchmark is from Section 7 of the 
>> BigTable paper "Bigtable: A Distributed Storage System for Structured Data", 
>> the benchmark task includes: random write, random read, sequential write, 
>> and sequential read. The test results made us puzzled. We use a cluster of 5 
>> nodes (each node has a 4 cores cpu , 4G memory).The data for test is a table 
>> with 4,000,000  records each of which is 1000 bytes. The test results are as 
>> follows:
>> Sequential write:  875124 ms
>> Sequential read:  1972588 ms
>> Random read:  43331738 ms
>> Random write:  20193484 ms
>> We wondered why the speed of sequential write are so faster than the speed 
>> of sequential read, and why the speed of sequential write are so faster than 
>> that of random write? We think that the speed of read should be faster than 
>> that of data write, but the results are just the opposite, would you please 
>> give us some explanations, thanks a lot!
>>
>> 2010-03-12
>>
>>
>>
>> Bingbing Liu
>>
>